A radical polymerization method has been a well-known method for polymerizing vinyl monomers to obtain a vinyl polymer. Generally, a radical polymerization method has the disadvantage of the difficulty in controlling the molecular weight of the obtained vinyl polymer. Further, there is the disadvantage that the obtained vinyl polymer is a mixture of compounds having various molecular weights, and thus it is difficult to obtain a vinyl polymer having narrow molecular weight distribution. Specifically, even if the reaction is controlled, the ratio of weight-average molecular weight (Mw) and number-average molecular weight (Mn), (Mw/Mn), can be only reduced to about 2 to 3.
As a method for eliminating the aforementioned disadvantages, since around 1990, a living radical polymerization method has been developed. Specifically, according to the living radical polymerization method, it is possible to control the molecular weight. It is also possible to obtain a polymer having narrow molecular weight distribution. Specifically, a polymer having Mw/Mn of 2 or less can easily be obtained. Therefore, this method has come into the limelight as a method for producing a polymer used in advanced technology such as nanotechnology.
Living radical polymerization methods are disclosed in, for example, patent documents 1-4 and non-patent documents 1-6, which are described later.
In order to perform living radical polymerization efficiently, conventionally, halogenated hydrocarbons or the like has been used as a so-called dormant species. However, in the case of using a halogenated hydrocarbon or the like as a dormant species, it is necessary to synthesize or obtain the halogenated hydrocarbon or the like in advance. Therefore, a process without the need of synthesis or the like of a dormant species has been desired.
Moreover, it is known that the living radical polymerization method can be used for manufacturing a polymer product of a complicated structure such as the so-called star-type polymer (FIG. 3), comb-type polymer (FIG. 4), and surface graft polymer (FIG. 5). Specifically, for example, there is a method of using a compound having a plurality of starting groups arranged so as to correspond to the polymer chain arrangement of a desired product. In such a case, in particular, preparation of the compound having the plurality of the starting groups is required, and thus it is disadvantageous in that the process as a whole is complicated.
On the other hand, in the living radical polymerization, it is also disadvantageous in that an expensive catalyst is needed in a large amount.
However, when such a transition metal complex catalyst is used, it is necessary to use a large amount of the catalyst. This is disadvantageous as it is not easy to completely remove the large amount of the catalyst used, from the products after the reaction. Another disadvantage is environmental problems which may occur by the disposal of the catalyst. The transition metal for the living radical polymerization method includes many toxic metals. The disposal of a large amount of such toxic metals causes environmental problems. Furthermore, there are cases where toxicities of catalysts remaining in products cause environmental problems. Due to the toxicity, it is difficult to use the transition metal catalysts for the production of food packages, material for living body, and medical material. Additionally, there is a problem associated with a high electroconductivity of the transition metal remaining in polymer, rendering the polymer conductive and hence unsuitable for use in electronic material such as resist material. Furthermore, the transition metal-type catalysts do not dissolve in a reaction solution unless they form a complex. Therefore, it is necessary to use a ligand as an additive to form a complex. This causes problems, i.e., an increase of the cost of production and also an increase of the total weight of the catalyst used. Further, a ligand is usually expensive and requires a complicated synthesis method. Furthermore, the polymerization reaction requires a high temperature (for example, 110° C. or higher). (For example, in aforementioned Non-patent document 1, the polymerization reaction is performed at 110° C.).
As mentioned above, conventionally, in order to conduct living radical polymerization efficiently, generally, a catalyst and a dormant species are used in combination.
For example, Patent Document 1 (Japanese Laid-open Publication No. 2002-249505) discloses that a complex, in which Cu, Ru, Fe, Ni or the like is a central metal, is used as a catalyst.
Further, Patent Document 2 (Japanese Laid-open Publication No. 11-322822) discloses that a hydrido rhenium complex is used as a catalyst and hydrocarbon halide is used as a dormant species.
Non-Patent Document 1 (Journal of The American Chemical Society 119, 674-680 (1997)) discloses that a compound in which 4,4′-di-(5-nonyl)-2,2′-bipyridine is coordinated with copper bromide, is used as a catalyst. In the case of the copper complex catalyst disclosed in Non-Patent Document 1, the catalyst cost needed for polymerization of 1 kg of a polymer is about several thousand yen.
It is noted that a living radical polymerization methods, which do not require a catalyst, have also been known. For example, a nitroxyl-type method and dithioester-type method have been known. However, these methods have the following disadvantages. A special protecting group (i.e., a certain nitroxide or dithioester group) must be introduced to the polymer growing chain. The protecting group is very expensive. Further, the polymerization reaction requires a high temperature (for example, 110° C. or higher). Further, the produced polymer is likely to have undesirable properties. For example, the produced polymer is likely to be colored differently from the natural color of the polymer. Further, the produced polymer is likely to have an odor.
On the other hand, Non-Patent Document 2 (Polymer Preprints 2005, 46(2), 245-246) and Patent Document 3 (Japanese Laid-open Patent Publication No. 2007-92014) disclose that compounds having Ge, Sn, or the like as a central metal are used as catalysts, and that hydrocarbon halide is used as a dormant species. Moreover, Patent Document 4 (International Publication WO2008/139980) discloses that a compound, having nitrogen or phosphorus as the central metal, is used as a catalyst.
Moreover, Non-Patent Document 3 discloses that a phosphorus compound is used as a catalyst and an organic halide is used as a dormant species.
As mentioned above, conventionally, it was technical common knowledge of those skilled in the art that in order to efficiently conduct living radical polymerization, a combination of a catalyst and a dormant species is used.
As the dormant species, alkyl halides and the like have been considered preferable, and an alcohol compound has not been considered usable as the dormant species.
On the other hand, in the research of a low molecular weight compound not related to the reaction for synthesizing a polymer, reaction of a halogen with various compounds such as alcohols has been studied.
For example, Non-Patent Document 4 describes a method for oxidation cyclization of mono-t-butyl dimethyl silylated diol. Although Non-Patent Document 4 discloses a reaction for iodizing the hydroxyl group of mono-t-butyl dimethyl silylated diol with N-iodosuccinimide (NIS) in the middle of a reaction, it does not disclose use of the reaction for a method other than the method for oxidation cyclization of mono-t-butyl dimethyl silylated diol. That is, its use for polymer synthesis is not described at all.
Moreover, Non-Patent Document 5 discloses that a mixture of diacetoxy iodobenzene ((AcO)2IPh) and I2 is used for intramolecular hydrogen abstraction in order to synthesize a cyclic ether with a satisfactory yield. Although Non-Patent Document 5 discloses the reaction wherein an alcohol is iodized by a mixture of ((AcO)2IPh) and I2, it does not describes that the reaction is used for a purpose other than the synthesis of a cyclic ether. There is no description that the reaction is used for polymer synthesis.
Moreover, Non-Patent Document 6 describes a method for synthesizing a benzisothiazolone compound. Non-Patent Document 6 describes that a reaction, in which an amine is iodized by a mixture of ((AcO)2IPh) and I2, is generated at the time of synthesizing an intermediate of the compound (Scheme 1). However, it does not describe that the reaction is used for a method other than the method of synthesizing the benzisothiazolone compound. That is, there is no description that it is used for polymer synthesis.
Furthermore, Non-Patent Document 7 describes a method for synthesizing γ-lactone or δ-lactone from an aromatic carboxylic acid. Non-Patent Document 7 describes that a ring can be formed using a hydrogen abstraction reaction and halogenation reaction at the time of synthesizing a lactone ring (Path A at page 7089), and a mixture of PhI(OCOCF3)2 and I2, a mixture of Hg(OAc)2 and I2, and a mixture of Pb(OAc)2 and I2 may be used as a reagent therefor (Table 3). However, it does not describe that the reaction is used for a method other than the method of synthesizing lactone. That is, there is no description that it is used for polymer synthesis.